That scenario played out yesterday at 10.20am at the construction site of 8 Riversuites condominium at Whampoa East. The crane was one of three at the site.

While operating his crane, the operator suddenly felt weak and couldn't muster the strength to scale down from the operator's cabin, which was then 40m high - about the height of a 13-storey building.

The crane operator had radioed his supervisor that he was feeling unwell, Mr Imran - who identified himself as a safety supervisor - told The New Paper.

The crane was not lifting anything at that time.

As the cabin was only accessible from the ground by the ladder along the mast, it meant the crane operator was stuck.

Mr Imran said: "(The crane operator) was unable to climb down the ladder on his own. He could not even stand up."

The operator had been well when he started work, said a project manager who declined to give his name.

The Singapore Civil Defence Force sent two fire engines, two fire bikes, two ambulances and three support vehicles to the scene and at least four Disaster Assistance and Rescue (Dart) Team members scaled the tower crane to assess the situation.

They found that the operator was not injured or trapped but simply too weak to make his own way down.

In an 80-minute operation, the Dart teamhelped the crane operator out of the operating cabin, secured him to a harness and brought him back to the ground. He was then taken to Tan Tock Seng Hospital. The construction company could not be reached for comment by press time.

(The crane operator) was unable to climb down the ladder on his own. He could not even stand up.